I think it's far more important to have good skills than to have a super computer, anyway we need a good computer to make our job and the great news is that today we can buy a very well performing machine at reasonable price.
Pretty often my students or my younger colleagues ask me what computer to buy to make their job, so I decided to select 3 laptops for 3d rendering covering different budgets. I picked them from Amazon since it's present worldwide, but you are free to order the same laptops for rendering from other sources:
LAPTOPS FOR 3D RENDERING?
If I have to choose between owing just a laptop or a desktop for 3d rendering I will always pick the laptop. That could sound strange to any nerd-3d-never-enough-power-hungry user, anyway my style of work relies more on software optimization and artistic knowledge than computational-brute-force approach.So if I need more power I can always rent a farm.
The laptop gives me a lot flexibility, I can work in office or at home, to the client base or in the airplane. Also, the compute-power difference compared to the desktops is not so huge (around 30% most of the time).
These are my picks, I won't spend money on cheap laptops because I can save $200/$300 to take a much worse laptop for rendering and graphic. I tested these laptops for rendering (I have one, the other two are own my by colleagues or students) and they are very good in many aspects (cpu and gpu power, display, storage, noise and heat). You can also upgrade them in future with more RAM or a new SSD (these laptops support 2 HDDs, which I think it is an essential feature). I used to buy Alienwares but today I think Asus has far more affordable and reliable laptops for rendering.
NOTE: CPU score is related to Cinebench R15 64-bit multi core render performance, GPU score is related to LUXMARK 2.0 sala benchmark. You can deepen the CPU and GPU performance aspects just doing some google research.